1. Field of the Invention
This invention relates primarily to homopolar dynamoelectric machinery, and more specifically, this invention relates to a segmented magnet homopolar dynamoelectric machine that utilizes a fluid cooled liquid metal current collecting arrangement.
2. Description of the Prior Art
Many types of homopolar motors and generators have been proposed and constructed in the past. These have included homopolar machines with segmented drums and discs, multi-layer drums, or single drums and discs. Conventional designs have required very large magnets to produce the large magnetic fluxes that link the armature conductors to produce therein the necessary voltages and currents.
Some attempts were made in the past to increase the output capabilities of homopolar machines by utilizing a multiplicity of magnetic poles along the axis of the machine. Examples of such attempts are illustrated in U.S. Pat. No. 339,772 -- Hering; U.S. Pat. No. 1,271,061 -- Morse; U.S. Pat. No. 1,327,349 -- Morse; and U.S. Pat. No. 1,327,350 -- Morse. While these patents do reveal the concept of utilizing multiple magnetic circuits to increase the power capabilities of homopolar dynamoelectric machines, no commercially feasible machine of this type has apparently ever been produced.
With the increasing attention being directed toward the use of superconductors, the utilization of super-conductive coils to provide the high fields needed in a homopolar dynamoelectric machine seems attractive. Efforts are presently being made to develop rotating disc and concentric drum homopolar machines utilizing single super-conductive magnets. The use of a single or double magnet with rotating drum armature machines is known. However, all such machines use large flux systems, with large air gaps, and consequently require high energy excitation systems.
In view of the significantly larger currents being produced by homopolar machines having superconductive magnets, the old mechanical brush method of transferring current from a moving to a stationary member became outmoded, as mechanical brushes can not handle the large current densities for any significant period of time. Thus, liquid metal current collecting arrangements have become necessary. Liquid metal current collection arrangements have the capability of handling high current densities, but the liquid metal has to operate in low flux fields to keep magneto-hydrodynamic losses in the liquid metal to a reasonable level. This means that unsaturated ferromagnetic material must be located in the vicinity of the current collection zone in order to protect the liquid metal from excessive magneto-hydrodynamic losses.
An example of the prior art single magnet structure utilizing a liquid metal current collecting arrangement is shown in the Aug. 12, 1971 issue of "The Engineer," pages 39-40. As in all examples of this type of machine, the machine is relatively large and heavy for the output powers obtained, a high energy excitation system is required to provide the necessary magnetic flux, and dissipation of the heat produced in the liquid metal current collecting arrangement is inadequate.